Endothelial cells and smooth muscle cells are the main cell types located in the intimal and medial layer of blood vessels and responsible for producing the extracellular supporting tissue and basement membranes. A proliferative response of these cells is a major feature of many vascular diseases (scleroderma, diabetes mellitus, arteriosclerosis). We propose to examine these cells in vitro for their capacity to produce and secrete various collagenous and non-collagenous proteins by using specific antibodies against these proteins. Techniques applied in these studies will include immonfluorescent, immunochemical, electrophoretic and chromatographic analyses and metabolic labeling in order to identify precursor forms of these proteins. Data obtained will be correlated with the distribution of these proteins in intact tissues. In a second stage, we will attempt to selectively suppress synthesis of discrete proteins by adding fragments of these proteins to the cultured cells. Precursor-specific fragments as shown recently for procollagen peptides are likely candidates for exerting this type of feed-back inhibition. Results obtained will be evaluated with respect to a potential therapeutic use of small protein fragments to manipulate matrix production of these cells in the diseased state.